As an owner of the older EX version, I find it curious that TDP claim the new one is "sharper". All the info we have suggests nothing has changed optically. Lensrentals even pulled them apart and the optical modules appeared identical. Is this "sample variation" at work?

I am a little confused. The Digital Picture review claims that this new S version shows a significant improvement in sharpness, and has the comparative test results to back this up. Yet the MTF charts and optical design for this lens and the previous version are identical. Also, Roger over at LensRentals (who I have a great deal of faith in) says: "the optics are identical" and consequently he wouldn't pay the extra grand for the new version.

I am a little confused. The Digital Picture review claims that this new S version shows a significant improvement in sharpness, and has the comparative test results to back this up. Yet the MTF charts and optical design for this lens and the previous version are identical. Also, Roger over at LensRentals (who I have a great deal of faith in) says: "the optics are identical" and consequently he wouldn't pay the extra grand for the new version.

What do you think is going on here?

Explained in article.

Roger, after tearing down both OS versions of the 120-300, said it appeared that elements in these lenses could be interchanged. The optical design seems unchanged. When questioned about this, Sigma replied that the 120-300 "S" has 2 FLD Glass elements instead of one. FLD glass has performance equal to fluorite, which is excellent.

Roger, after tearing down both OS versions of the 120-300, said it appeared that elements in these lenses could be interchanged. The optical design seems unchanged. When questioned about this, Sigma replied that the 120-300 "S" has 2 FLD Glass elements instead of one. FLD glass has performance equal to fluorite, which is excellent.

So 2 FLD elements instead of one so better IQ.

One major problem with that... if you look back to the older one, Sigma says that has two FLD elements, and further references to this can be found in various reviews like at photozone and lenstip. The only way this unspecified source at Sigma could be right now is if Sigma were originally lying about having two SLD elements. Doesn't add up.

I'd speculate it could still be down to sample variation, especially if Sigma have tightened up their build quality.

Canon's current 70-300L is a great lens but a bit slow. Fixed F4 would make this a real winner and a great alternative to the 200-400 on a APS-C body.

Well, see it the other way around: The 70-300L is a f5.6 lens with added f4 at the wide end :-) ... it's a zoom after all. If it would be constant aperture it'd have to be much heavier, most likely a good deal more bulky and surely more expensive, which would deprive the 70-300L of the defining characteristic "flexible, sturdy, ok iq & still portable".

I had an OS mk 1 for a while. It's certinly a sharp lens, nearly as sharp as a prime wide open. Excellent still with a 1.4x and a little softer with a 2x. Mine needed a fair bit of MA to coax the best out of it. I found that the focal drop at MFD to be quite alarming (beyond what I've experianced with other zoom lenses) and I found the AF to be fast (but slower than Canon's finest) but a little erratic. When I popped a 2x TC on it (theoretically a 600mm FL) and popped it along side my 400L. At 3m focus I found that their focal lengths were nearly identical. So when I put all this togther and considered the vast size and weight, I figured I was better off with a 70-200 f2.8 L IS II and a 1.4x TC or a 400L. But that was my findings! If you like this lump, go for it, it's your money!

I had an OS mk 1 for a while. It's certinly a sharp lens, nearly as sharp as a prime wide open. Excellent still with a 1.4x and a little softer with a 2x. Mine needed a fair bit of MA to coax the best out of it. I found that the focal drop at MFD to be quite alarming (beyond what I've experianced with other zoom lenses) and I found the AF to be fast (but slower than Canon's finest) but a little erratic. When I popped a 2x TC on it (theoretically a 600mm FL) and popped it along side my 400L. At 3m focus I found that their focal lengths were nearly identical. So when I put all this togther and considered the vast size and weight, I figured I was better off with a 70-200 f2.8 L IS II and a 1.4x TC or a 400L. But that was my findings! If you like this lump, go for it, it's your money!

But what about at distances farther away than 3 meters? Surely most people who would use this lens with a 2x TC, will be shooting things farther away than that?

I had an OS mk 1 for a while. It's certinly a sharp lens, nearly as sharp as a prime wide open. Excellent still with a 1.4x and a little softer with a 2x. Mine needed a fair bit of MA to coax the best out of it. I found that the focal drop at MFD to be quite alarming (beyond what I've experianced with other zoom lenses) and I found the AF to be fast (but slower than Canon's finest) but a little erratic. When I popped a 2x TC on it (theoretically a 600mm FL) and popped it along side my 400L. At 3m focus I found that their focal lengths were nearly identical. So when I put all this togther and considered the vast size and weight, I figured I was better off with a 70-200 f2.8 L IS II and a 1.4x TC or a 400L. But that was my findings! If you like this lump, go for it, it's your money!

But what about at distances farther away than 3 meters? Surely most people who would use this lens with a 2x TC, will be shooting things farther away than that?

It all depends on what you are photographing. If you want a diffused background and you are photographing wildlife, then the subject needs to be close to decouple the background. If you are in a hide or shooting from along way away then sure it's a fine lens for that.

My biggest (and only one so far) concern is about the reach. I've read a couple of times that the Siggy is shorter @ 300mm than the canon fixed 3002.8ISII. Those reviews were about the previous model of 120-300 but it ain't supposed to be optically different from the brand new one.

If this was real, the Sigma wouldn't be as interesting as it seems...Ideally i'd buy it to complement my 70-200 as the 120-300 remains really cheaper than the Canon 300mm and i often need an extra reach that a 300mm (or 420 with 1.4x) would bring me.

Anyone ? Have you ever heard any kind of complaints like this ?Does anyone could compare the reach of the 120-300 to the 300L ?

"...Siggy is shorter @ 300 than the canon..."

It irritates me when people make confusing statements like this without stating what focus distance they are referring to.

I suspect that focussing at "infinity" ie in practice say 200 to 300 metres and beyond the new Sigma is probably a true 300 lens. However it seems to be the case that at close focus zooms generally loose focal length faster that primes.

The same used to be said of the 100-400L. I once carefully compared image size of a 100-400L @ 400 with the Canon 400/5.6 using same camera focussed on a distant building and guess what - the image size was exactly the same ie my 100-400L was a true 400 at distance.

The big problem is the weight: as TDP writes "There is no question that this lens can be handheld and that OS aids in doing so – but such use will be avoided most of the time by all but the strongest photographers. " It weighs a full kilo more than the Canon 300mm f/2.8 II and 200g more than the 500mm f/4 II. I tried it out and found it far too heavy for hand holding for me. Also, the IQ is ruined by a 2xTC, unlike that of the 300mm prime.